Method for forming lubricant coatings on metal surfaces to be deformed

ABSTRACT

A PROCESS FOR FORMING A LUBRICANT COATING ON A METAL SURFACE TO BE DEFORMED WHEREIN A PHOSPHATE MATERIAL IS APPLIED TO THE METAL SURFACE SO AS TO EFFECT A CONTROLLED REACTION BETWEEN THE PHOSPHATE MATERIAL AND THE METAL SURFACE AND FORM A PHOSPHATE COATING WHICH IS AT LEAST PARTIALLY UNREACTED WITH THE METAL SURFACE. THEREAFTER, A FATTY ACID COMPOSITION IS APPLIED TO THE PHOSPHATE COATED SURFACE SO AS TO EFFECT A CONTROLLED REACTION BETWEEN THE FATTY ACID COMPOSITION AND THE PHOSPHATE COATING AND FORM A FATTY ACID COATING WHICH IS AT LEAST PARTIALLY UNREACTED WITH THE PHOSPHATE COATING AND THE METAL SURFACE. BOTH THE PHOSPHATE MATERIAL AND THE FATTY ACID COMPOSITIONS ARE APPLIED SO THAT A SUBSTANTIALLY DRY COATING IS FORMED SUBSTANTIALLY UPON CONTACT OF THE RESPECTIVE MATERIAL WITH THE METAL SURFACE. PREFERABLY, THE METAL SURFACE IS AT AN ELEVATED TEMPERATURE WHEN THE COATING MATERIALS ARE APPLIED AND BOTH THE PHOSPHATE MATERIAL AND THE FATTY ACID COMPOITION ARE DESIRABLY IN THE FORM OF AQUEOUS SOLUTION.

3,556,867 METHOD FOR FORMING LUBRICANT COATINGS ON METAL SURFACES TO BE DEFORMED Cecil W. Glasson, Huntington Woods, Mich., assignor to Hooker Chemical Corporation, Niagara Falls, N.Y., a corporation of New York No Drawing. Continuation-impart of application Ser. No. 649,139, June 27, 1967. This application Apr. 18, 1968, Ser. No. 722,148

Int. Cl. C23f 7/10 US. Cl. 1486.15 12 Claims ABSTRACT OF THE DISCLOSURE A process for forming a lubricant coating on a metal surface to be deformed wherein a phosphate material 15 applied to the metal surface so as to effect a controlled reaction between the phosphate material and the metal surface and form a phosphate coating which is at least partially unreacted with the metal surface. Thereafter, a fatty acid composition is applied to the phosphate coated surface so as to effect a controlled reaction between the fatty acid composition and the phosphate coating and form a fatty acid coating which is at least partially unreacted with the phosphate coating and the metal surface. Both the phosphate material and the fatty acid compositions are applied so that a substantially dry coating is formed substantially upon contact of the respective material with the metal surface. Preferably, the metal surface is at an elevated temperature when the coating materials are applied and both the phosphate material and the fatty acid composition are desirably in the form of aqueous solution.

This application is a continuation-impart of my copending application Ser. No. 649,139, filed June 27, 1967, now abandoned.

This invention relates to a method for producing a lubricant coating on a metal surface to be deformed and more particularly, relates to a process for forming a phosphate-soap lubricant coating which may be easily removed from the metal surface after deformation.

In processes for the cold forming of metal, such as metal deformation and drawing, it is the practice to provide a lubricant coating on the metal surface which is to be deformed. In many instances, the metal surface is first provided with a chemical coating, such as a phosphate coating, sulfide coating, oxide coating, oxalate coating, or the like. Thereafter, a coating of an organic lubricant material, such as an oil, wax or preferably, a soap, such as a fatty acid soap, is applied to the chemically coated metal surface. Typically, both of the coating materials are applied to the metal surface using conventional application techniques, such as immersion, spray coating, roll coating, or the like. As is known in the art, phosphate coating compositions applied in this manner react with the metal surface, such as a ferrous metal surface, forming a mixed iron and zinc phosphate coating on the surface, where, for example, a zinc phosphate coating composition is used. Similarly, the fatty acid soap compositions applied in this manner normally also reacts to some extent with the phosphate coating, forming a metal salt of the fatty acid, such as a mixed zinc and iron stearate, Where, for example, the fatty acid soap is a sodium soap of stearic acid.

Although the coatings produced in the above manner form a continuous unctuous film which provides an excellent parting layer between the metal and the die during the deforming operation, removal of these coatings after the metal has been deformedhas presented some difficulties. Generally, because of the extent of the reaction of United States Patent the chemical coating material, such as the phosphate, material, with the metal surface and the extent of the subsequent reaction of the soap composition with the phosphate material, a series of alkaline and/or acidic washes have frequently been necessary in order to obtain a surface which is sufficiently clean for further processing, as for example, for plating.

It has further been found that with the application techniques which have heretofore been used, it has often been very difficult, if not impossible, to maintain a close control on the coating Weight of the chemical coating materials and soap lubricant materials which are applied. This is undesirable in that the application of too heavy lubricant coatings result in the buildup of excess lubricant in the die, while the application of insufficient lubricant frequently results in imperfectly formed or defective parts or even die breakage. Moreover, in the heretofore utilized application techniques, it has generally been necessary to provide extensive dry-off ovens or areas in order to obtain substantially complete drying of the lubricant coating on the metal surface. Where such drying is not effected, rusting of the lubricant coated metal parts is often encountered if the parts are stored for any appreciable period of time after lubing and before they are deformed.

It is, therefore, an object of the present invention to provide an improved method of forming a lubricant coating on a metal surface to be deformed, which coating is readily removed from the formed part.

Another object of the present invention is to provide a method for forming a lubricant coating on metal surfaces to be deformed whereby the amount of lubricant applied can be closely controlled.

A further object of the present invention is to provide an improved process for deforming metal, utilizing the lubricant application method as has been indicated here: inabove.

These and other objects will become apparent to those skilled in the art from the description of the invention which follows.

Pursuant to the above objects, the present invention includes a process for treating a metal surface to form thereon a lubricant coating suitable for use in a metal forming operation, which process comprises applying a phosphate material to the metal surface, effecting a controlled reaction between the phosphate material and the metal surface to form a phosphate coating which is at least partially unreacted wth the metal surface, the application of said phosphate material being carried out so as to form a substantially dry coating, substantially upon contact with the metal surface, applying a fatty acid soap composition to the thus-coated surface and effecting a controlled reaction between the soap composition and the phosphate coating to form a soap coating'which is at least partially unreacted with the phosphate coating and the metal surface, the application of the soap composition being carried out so as to form a substantially dry coating, substantially upon contact with the surface. The application of the coating material by the above method may, be controlled to obtain a desired coating weightl on th e surface and the residual coating remaining onthe metal surface after the deforming operation is easilyremoved.

More specifically, inthe practiceof the rneth od oflthe present invention, the phosphate material. whichtis. first applied to the metal surface towbe deformed is 'preferably an aqueousphosphate-containingsolution.Various solutions of this type, as are known to..tho"se 'in theLart; may be used, including aqueous:solutions of'alkali metal phosphate and aqueous acidic solutionsof'variousmetal I phosphates, such as zinc phosphatesymanganese phosphates, and the like. Of these, the preferred-are theaque ous acidic phosphate solutions,.withi aqueous acididiinb phosphate solutions being particularly preferable. These solutions typically have a pH within the range of about 1.3 to 5.0 and contain zinc ions and phosphate ions in amounts within the range of about 1 to 15 grams per liter and 6 to 45 grams per liter, respectively. As is known to those in the art, these solutions may be formulated from any convenient source of zinc and phosphate ions such as zinc oxide and phosphoric acid, as well as from other zinc and phosphate-containing materials, so long as the ions added with the zinc and phosphate are not detrimental to either the coating solution itself or to the coating which is produced.

In addition to the zinc ions and phosphate ions, these treating solutions may also contain other materials, such as nickel ions, nitrate ions, and the like. Where such additional ions are present, they are desirably used in amounts up to about 12 grams per liter, with amounts within the range of about 0.1 to 5.0 grams per liter being preferred. In a most preferred embodiment of the present invention, the phosphate composition contains the following components in the amounts indicated:

Components: Grams per liter Zinc l to 15 P 6 to 45 Nickel 0.1 to Nitrate 0.5 to 8 Various fatty acid soap lubricant compositions may be used in the present method, including those based on an alkali metal soap of a fatty acid containing from about 8 to 22 carbon atoms. Desirably, these compositions are aqueous solutions containing the fatty acid soap, per se, as well as compositions which contain components which react to form the soap in situ in the composition, such as compositions containing a fatty acid, fat or an oil, and an alkaline material such as a metallic hydroxide or carbonate. A lubricant concentrate composition which has been found to be particularly useful in one which is an admixture of from about 3 to 75% by weight of an alkali metal pyrophosphate or an alkali metal tetraborate, from about 15 to 97% by weight of a soap of a fatty acid and water in an amount up to about 80% by weight of the composition, wherein at least 0.2% by weight of the lubricant composition, but less than 50% by weight of the soap present in the composition is a fatty acid soap selected from the group consisting of fatty acid soaps of lithium, potassium, ammonium, calcium, magnesium, zinc or aluminum, the remainder of the fatty acid soap being a fatty acid soap of sodium. Lubricant concentrate compositions of this type are described in US. Pat. 3,313,729, issued Apr. 11, 1967, the disclosure of which patent is hereby incorporated in the present specification. A particularly preferred composition of this type contains the following components in the amounts indicated:

Components: Percent by weight Sodium tallow soap 74.5 Tetrapotassium pyrophosphate 25.0

Lithium stearate 0.5

The soap lubricant concentrate compositions of this type are desirably dissolved in water in amounts sufficient to form an aqueous working lubricant composition having a viscosity which is suitable for spraying. Desir'ably, however, the 'viscosity of the working lubricant ,eompositionis as high as possible, while still permitting spraying, as the use of extremely dilute solutions of low viscosity necessitates the application of greater amounts of solution in order to obtain the desired coating weights on the metal surface. Typically, the working lubricant compositions used will'contain the concentrate material in amounts within the range of about 0.1 to 4 pounds per gallon, with amounts within the range of about 0.5 to 2 pounds per gallon being preferred. When using the specifically preferred lubricant composition as described hereinabove, a working lubricant solution containing the concentrate in an amount of about 1 pound per gallon has been found to give excellent results. Although the viscosity of the working lubricant composition will, of course, vary depending upon the concentration of the component, as well as the nature of these materials and the application technique used, in many instances, aqueous working lubricant compositions, of the above type, having a viscosity within the range of about 2000 to 10,000 centipoises have been found to be particularly useful.

In the practice of the present method, the phosphate composition and the soap composition may be applied in any convenient manner which will produce a substantially dry coating and which will effect the controlled reaction of the coating materials to form a coating which is at least partially unreacted with either the metal surface or the other coating material. In this regard, it is to be noted that in referring to the production of a substantially dry coating, it is intended to mean that there is substantially no migration of the coating components of the compositions applied, i.e., the phosphate material or the soap material, once the composition has been brought into contact with the surface to be treated. Thus, there is substantially no runoff of the overspray material and the coating components of the composition applied remain substantially in the area of the surface which they originally contact.

Additionally, where reference is made to effecting a controlled reaction between the coating material and the substrates to which they are applied, it is intended to mean that the application of the coating material is carried out in such a manner that a substantial amount of the coating material applied does not react with the substrate to which it has been applied. Desirably, this control of the reaction between the coating material and the substrate is effected by controlling the rate of dehydration of the solutions of the coating materials from the substrate after application. Such control may result by the control of the quantity of the coating solutions applied and/or control of the amount of heat which is available to effect the dehydration. Thus, in the application of the present coating material, the reaction of these materials with the substrate is controlled to the extent that the resulting coating is at least partially unreacted with the substrate and that the amount of reaction obtained is less than that which is normally obtained in the conventional application of these coating materials. Thus, for example, with the application of the phosphate coating materials, the application is carried out so that there is a controlled metal loss from the metal substrate to which the phosphate coatings are applied, which metal loss is less than that which is normally obtained when the materials are applied in conventional manner, as for example, by spraying, immersion, or the like techniques. In the present method, the reaction of the phosphate coating materials with the metal substrate is controlled to the extent that, desirably, there is a maximum weight loss of the substrate of less than about milligrams per square foot, and preferably less than about 60 milligrams per square foot. Similar controls of the reaction of the fatty acid soap lubricant materials are also effected.

Any suitable application technique which will give this substantially dry coating of the coating materials applied and Where the coatings produced are at least partially unreacted, either with each other or the metal surface as has been described, may be used. In general spray type applications, and particularly those wherein the materials applied are in a relatively finely divided state or mi-s are preferred. In many instances, the use ofgas atomized spray techniques have been found to give particularly satisfactory results and, for this reason, at the present time such application techniques arepreferred. It is to be appreciated, however, that in some instances,

otherspray techniques which will give similar coatings may also be used, such as airless spraying, electrostatic spraying, and the like.

When using the preferred gas atomized spray application technique, the preferred atomizing gas used is air, although other suitable atomizing gas which will not adversely aifect the materials being applied may also be used. In such applications, the coating material to be applied is pumped under pressure through a suitable nozzle from which it is atomized and sprayed with air also under pressure. For the application of the phosphate coating material, it has been found that material pressures within the range of about 3 to 30 pounds per square inch are desirable, with pressures within the range of 5 to pounds per square inch being preferred. Additionally, the pressure of the atomizing air for these phosphate materials is desirably within the range of about 10 to about 60 pounds per square inch with pressures within the range of about 10 to about 30 pounds per square inch being preferred. Similarly, for the application of the soap lubri cant composition, material pressures within the range of about 3 to about 30 pounds per square inch have been found to be desirable with pressures within the range of about 5 to pounds per square inch being preferred. The atomizing air pressures for the soap composition materials have desirably been found to be Within the range of about 10 to 60 pounds per square inch, with pressures within the range of about 12 to 30 pounds per square inch being preferred.

It will, of course, be appreciated that in each instance, the material and atomizing gas pressures which are used will depend upon the particular conditions of that application. Thus, the choice of the pressures used will depend upon the viscosity of the compositions being applied, the coating weight which is desired, as well as the number and placement of the spraying nozzles with respect to the metal surface which is to be coated. Accordingly, depending upon the particular combination of the above factors which are used, in some instances material pressures and atomizing gas pressures which are outside of the typical ranges which have-been set forth hereinabove may also be used.

Desirably, the metal surface to be treated is in the form of metallic sheet or strip, and preferably a ferrous metal sheet or strip, although other metals may also 'be treated. It is preferred that the metal sheet or strip be at an elevated temperature, in order to expedite the forming of a substantially dry coating of the material applied on the metal surface. Desirably, the metal surface is at a temperature of at least about 60 degrees centigrade with temperatures within the range of about 70 to 120 degrees cent :grade being preferred. If desired, the metal surface may be preheated prior to the application of the coating materials so as to be at the preferred elevated tempera ture when the materials are applied. Where, however, the metal sheet or strip has been subjected to a polishing operation, it has frequently been found that the temperature of the metal will be raised sufficiently during this operation so that a separate preheating of the metal is not necessary, and the application of the coating material may be carried out on the metal as it leaves the flat. polisher. In this regard, it has found that while in-the prior art processes, it is generally necessary to subject the metal from the flat polisher to an alkaline cleaning step, followed by a water rinse, in many instances, when using the present process, the alkaline cleaning and water rinse may be eliminated and the phosphate coating materialapplied to the metal from the flat polishing operation without any intermediate cleaning or rinsing operation. This is, of course, advantageous in that it reduces both the processing time required as well as the'ar nount of processing equipment and space for the installation of the treating line.

It is furtherto be appreciated, that in addition to heating the metal sheet or strip prior to the application of the various coating compositions, other means may also be utilized to provide the necessary amount of heat to obtain the desired substantially dry coating on the metal surface. Thus, for example, the coating solutions, themselves, may be heated at the time of their application, or heated gas, such as air or steam, may be directed over the surface of the metal as the coating materials are applied so as to effect the control of the rate of dehydration of the coating solutions from the metal surface. Obviously, of course, a combination of one or more of these techniques may be used, in conjunction with the control of the quantity of coating solutions applied, depending upon the specific conditions involved in each particular instance.

As has been noted hereinabove, the phosphate composition is applied to the metal surface to be treated prior to the application of the soap composition. Although, if desired the phosphate coating solution may be applied manually using an air atomized spray gun, it is preferred that the metal surface be passed through a spray zone containing a number of air atomized spray nozzles. The number of such nozzles used will, of course, depend upon the width of the metal sheet or strip to be coated, as well as the particular spray pattern and the placement of the nozzles which are used. Desirably, the spray nozzles are positioned in the spray zone so that substantially complete coverage of the metal surface is obtained in a single pass through the spray zone. In a typical installation, wherein steel sheet having a width of 20 inches is to be coated, 5 nozzles, giving a flat spray pattern with a length of 6" and a width of 2", are used, which nozzles are positioned about 7 inches away from the metal sheet.

Following the application of the phosphate material to the metal surface, the coated metal is passed substantially immediately to a second spray zone wherein the soap composition is applied in the same manner as the phosphate material. It is to be appreciated that although both the phosphate material and the soap composition may *be applied to only one side of the metal sheet or strip at a time, the other side being coated in a subsequent pass through the two spray zones, it is preferable if the spray nozzles are positioned so that both the top and bottom of the metal strip are coated simultaneously. In this manner, the complete formation of the lubricant coating on the metal is affected in a single pass through the two spray zones.

Although specific reference has been made hereinabove to the application of a phosphate coating material to the metal surface to be treated, it is to be appreciated that other coating materials may also be used which will produce a similar, substantially dry, coating which is at least partially unreacted with the metal surface. Similarly, other lubricant type materials than the soap compositions which have been specifically referred to hereinabove, may also be used, again provided that the coatings produced are substantially dry, and at least partially unreacted with either the metal surface or the previously applied phosphate or similar coating. Additionally, it is to be further appreciated that although specific reference has been made to the application of these coating compositions by means of air atomized spray, other application techniques which produce comparable coatings may also be used. In this regard, it isfound that the application of the coating materials so as to produce a spray in which the sprayed particles range in size from .00001 .inch to about .002 inch in diameter is typical of the characteristics of the spray which may be used to obtain the desired coating.

In order that those skilled in the art may better understand the present invention and the manner in which it maybe practiced, the following specific examples are given. In these examples, unless otherwise indicated, .temperatures are in degrees centigrade and parts and percent are by weight. It is to be appreciated, however, that these examples are merely exemplary of the present invention and are not to be'taken as a limitation'thereon.

7 EXAMPLE 1 A zinc dihydrogen phosphate solution was prepared which contained the following components in the amounts indicated:

Polished steel bumper blanks, 30% inches wide by 89 inches long by 0.94 inch thick, directly from the polishing machine at a temperature of 75 degrees centigrade, were then passed through a 4-foot spray zone at a conveyor speed of 50 feet per minute. Within this spray zone, the phosphating solution, at a temperature of 18 degrees centigrade, was sprayed on both the top and bottom of the sheet, by means of an air atomized spray nozzle, three nozzles being directed at both the top and bottom of the sheet. The material pressure for the spray nozzles was 7 pounds per square inch and the atomizing air pressure used was 12 pounds per square inch. The time for each of the blanks to pass through the spray zone was 4.8 seconds. Thereafter, the coated work was passed through a 3-foot reaction zone maintained at room temperature, the time for passage through this zone being 3.6 seconds. Thereafter, the sheets were passed through a second 4-foot spray zone wherein a lubricant solution containing 339 grams of tallow soap, 113 grams of tetrapotassium pyrophosphate, 2 grams of lithium stearate and suflicient water to make one gallon was sprayed on the top and bottom of the sheets, at a temperature of about 18 degrees centigrade. As in the previous spray zone, the lubricant solution was sprayed simultaneously on the top and bottom of the blank using five top and five bottom spray nozzles. The spray nozzles used were air atomized spray nozzles wherein the material pressure was 10 pounds per square inch and the atomizing air pressure was 15 pounds per square inch. The time for passage of the sheets through the second spray zone was 4.8 seconds. The hot, dry, coated sheets were then unloaded from the conveyor and stacked. It was found that the combined weight of phosphate coating and lubricant on the sheets was within the range of about 100 to 150 milligrams per square foot. The coated sheets were then formed into bumpers, using the regular production presses after which, the formed bumpers were cleaned with water only and were satisfactorily plated using regular production operations.

EXAMPLE 2 The procedure of Example 1 was repeated using a material pressure of 5 pounds per square inch for the phosphate material and an atomizing air pressure of pounds per square inch and using a material pressure of 11 pounds per square inch for the lubricant and an atomizing air pessure of 21 pounds per square inch. Using this procedure, it .was found that the combined weight of phosphate coating and lubricant formed on the sheets was within the range of 60-90 milligrams per square foot. These sheets, like those produced in Example 1, were satisfactorily formed into bumpers and plated, using normal production methods, with only a cleaning with water between the forming and plating operations.

EXAMPLE 3 The procedure of Example 1 was repeated with the exception that the material pressure and atomizing air pressure for the phosphate were 10 and 15 pounds per square inch, respectively and the material pressure and atomizing air pressure for the lubricant were 13 and pounds per square inch, respectively. Using this procedure a combined phosphate and lubricant coating of 140-200 milligrams per square foot was formed on the sheets, which sheets were formed into bumpers, cleaned with water and then plated, using normal production methods.

Examination of the coatings formed in each of the preceding examples indicates that in each instance, the coatings were only partially reacted with the metal and/ or each other.

While there have been described various embodiments of the invention, the compositions and methods described are not intended to be understood as limiting the scope of the invention as changes therewithin are possible and it is intended that each element recited in any of the following claims is to be understood as referring to all equivalent elements for accomplishing substantially the same results in substantially the same or equivalent manner, it being intended to cover the invention broadly in whatever form its principle may be utilized.

What is claimed is:

1. A method for treating metal surfaces to form thereon a lubricant coating, suitable for use in metal forming operations, which comprises applying a phosphate material to the metal surface, effecting a controlled reaction between the phosphate material and the metal surface, by controlling the rate of dehydration of the phosphate material from the metal surface, forming a phosphate coating which is at least partially unreacted with the metal surface, the amount of reaction with the metal surface being such that upon removal of the phosphate coating, the metal loss from the surface is less than about milligrams per square foot, the application of said phosphate material being carried out so as to form a substantially dry coating, substantially upon contact with the surface, applying a fatty acid soap composition to the thus-coated surface and effecting a controlled reaction between the soap composition and the phosphate coating to form a soap coating which is at least partially unreacted with the phosphate coating and the metal surface, the application of the soap composition being carried out so as to form a substantially dry coating, substantially upon contact with the surface.

2. The method as claimed in claim 1 wherein the application of the phosphate material and the fatty acid soap composition is effected by means of a gas atomized spray.

3. The method as claimed in claim 2 wherein the atomizing gas used is air.

4. The method as claimed in claim 3 wherein the air atomized spray application of the phosphate material is carried out at a material pressure within the range of about 3 to 30 pounds per square inch and an atomizing air pressure within the range of about 10 to 60 pounds per square inch and the air atomized spray application of the fatty acid soap composition is carried out at a material pressure within the range of 3 to 30 pounds per square inch and an atomizing air pressure within the range of about 10 to 60 pounds per square inch.

5. The method as claimed in claim 4 wherein the phosphate material and the fatty acid soap composition applied are aqueous solutions.

6. The method as claimed in claim 5 wherein the phosphate material contains the following components in the amounts indicated:

and the fatty acid soap composition is formed from a concentrate which contains the following components in the amounts indicated:

Sodium tallow soap 15-95% by weight.- Tetrapotassium pyrophosphate 3-75 by weight. Lithium stearate 0.2 to not more than 50%, by weight of the soap present.

Grams/liter Zn 1-15 P 6-45 Nickel 0.1- N0 0 5-8 and the coating of the fatty acid soap composition is formed by applying an aqueous composition formed from a concentrate containing the following components in the amounts indicated:

Sodium tallow soap -97 by weight.

Tetrapotassium pyrophosphate 3-75 by weight.

Lithium stearate 0.2 to not more than 50% by weight of the soap present.

9. A method of deforming metal which comprises forming a lubricant coating on the metal surface to be deformed in accordance with the method of claim 1 and, thereafter, deforming the thus-coated metal surface.

10. The method as claimed in claim 9 wherein the lubricant coating is formed by the sequential air atomized spray application of a phosphate material and a fatty acid soap composition.

'11. The method as claimed in claim 10 wherein the air atomized spray application of the phosphate material is carried out at a material pressure within the range of about 3 to pounds per square inch and an atomizing air pressure within the range of about 10 to 60 pounds per square inch and the air atomized spray application of the fatty acid soap composition is carried out at a material pressure within the range of about 3 to 30 pounds per square inch and an atomizing air pressure within the range of about 10 to 60 pounds per square inch.

12. The method as claimed in claim 11 wherein the phosphate material is an aqueous solution containing the following components in the amounts indicated:

Grams/liter Zn 1-15 P0 6-45 Nickel 01-5 N0 0 5-8 and the fatty acid soap composition is an aqueous composition formed from a concentrate containing the following components in the amounts indicated:

Sodium tallow soap 15-97% by weight. Tetrapotassium pyrophosphate 3-75 by Weight. Lithium stearate 0.2 to not more than by weight of the soap present.

References Cited UNITED STATES PATENTS 2,921,865 1/1960 Kubie 148-6.15X 3,203,835 8/1965 Blum 148-615 3,240,633 3/1966 GoW-man et al 1486.15 3,313,728 4/1967 Glasson et a1. 117-134 3,380,859 4/1968 Pell 148-615 OTHER REFERENCES Schuster: Abstract of application 37,498, filed July 7. 1948, published NOV. 30, 1951.

RALPH S. KENDALL, Primary Examiner US. Cl. X.R. 7242, 46; 117134 

